Another Japanese page (
http://eaglet.skr.jp/MILITARY/74.htm) claims:
Type 74B: 1984 -- Improved FCS to support Sabot Rounds.
Type 74C - 1987. Two color camouflage
Type 74D - 1987. Thermal Sleeve.
Type 74E: - 1991; Improved FCS to support Type 91 HEAT-MP in 1991.
Type 74F - 1993, Mine Roller.
I'll leave it up to you as to how to integrate the differing claims between my prior research posts.